Work holding chuck



Oct. l1, 1960 G. F. BREwsTER 2,955,829

WORK HOLDING CHUCK Filed July 16, 1958 2 Sheets-Sheet 1 l NVENTOR sf asFlG. 4- Y ATTORNEY Oct. l1, 1960 G. F. BREwsTER 1 2,955,829

' WORK HOLDING CHUCK Y Filed July 16, 1958 2 Sheets-Sheet 2 INVENTOR,Lw/Zi ATTORNEY Patented Oct.l 1,1,

2,955,829 WORK HoLDlNG CHUCK George F. Brewster, Ford Lane, Kittery,Maine Filed July 16, 1958,7Sel'. N0. 748,895

3 Claims. (Cl. 279`3.)

The present invention relates to an -i1nprovedwork Iholding chuck of thevacuum operated type for use in Y' holding surfaces of workpieces whichare to be 'subjected -to various machining operations, or possibly othertreatment or examination. This invention is an improvernent on thevacuum chuck described and claimed in UgS. Patent No. 2,730,370 issuedto me January 10, 19156.

In the earlier form of invention disclosed in this `vpatent means wereprovided for supporting an elastic sealing ring of toric cross section,in a workholding .element in such a position that suction forces couldbe exerted within the area defined by the sealing ring for a number oftypes of workpieces to be dealt with. This form of suction has beenfound to be highly satisfactory. However, in certain other classes ofwork such as pieces 'of annular form or some other shape involving fa-hol'eat or near the center, lthe chuck ofthe patent could not be usedsince the necessary suction forces could not be eX- ertred where a holewas present.

The present invention is concerned with the problem indicated Vand aimsto provide an improved method and Vapparatus of the vacuum operated typefor holding workpieces. It is especially an object of -the invention todevise `a unitary sealing ringand cooperating sealing groove forproviding in a workholding element -asuitable gripping action eitherexternally or internally o'f an annular workpiece. It is further anobject 'of the invention "to combine with this specially devised form of'sealingmeans selectively controlled suction means for exerting suctionforces from points either internally or externally'of respective areasof the sealing ring. t i' 7 These and other objects `and novel featureswill be more fully understood and appreciated from the followingdescription of a preferred embodiment Vof the invention selected forpurposes vof illustration 'and 'shown in the accompanying drawings, inwhich:

Fig. 1 is Aa plan view -of the improved chuck of the invention;

Fig. 2 is a cross section taken on Fig. 1;

Fig. 3 is an enlarged cross section generally ACorresponding to thestructure shown -in Fig. 2, vbut indicating van annular workpiece in avacuum heldposition;

Fig. 4 is still another Venlarged detailed -cross section showinganother position ofthe chuck mechanism; and

Fig. 5 is an enlarged cross sectional detailed view of the `line of Vthering retaining groove of the invention.

The present invention is based on the novel concept of utilizing anelastic sealing ring fof the same general toric -cross section asdescribed in my patent noted above. This ring may be supported toprovide a seal 'for'various 'types of workpieces including a' workpiecewfhbllf? 5.11.51@ at or near its center. Two of these rings may 'be usedto secure a workpiecewith a .hole rin its cen-ter.

I iindthis concept of utilinngone type of elastic sealing ringfor'fde'alng'with two d-ierent classes of workpieces may be practicallyrealized .by containing the elasfticring in a work holdingJe'le'rnent,presentinga flat ace 'which :is recessed 'to 'provide "specialringr'retjaining grooves. Each ring retaining groove is designeditosplrt the elastic sealingri'ng a position such thatfafp'art V "of the'sealing ring projects 'slightly 'above the vrfate' of 'the fug vthesealing ring in the position described. Immedifately below these spacedcylindrical surfaces are twordouble curved surfaces and at the bottom ofthegroove is still .a third double curved surface. The two double curvedsurfaces constitute inner and outer toresealing surfaces'generated bythe revolution of a conic about .an axis which lies in its plan; whichis parallel to the -iat face; and which is located below the flat face,a distance less than the radius of the conic. The space between double.curved surfaces is chosen of a magnitude corresponding tothe diameterof the toric section of the sealing'ring, thus when the sealing ring hasbeen forced .into the 'entering opening it may vbe crowded down into.space between thetwo double curved sealing surfaces 'and ,willcompletely Vlill this portion of the groove. The bottom double ycurvedsurface is generated by revolution of a conic whose axis lies below theaxis of thedouble `curved surfaces and thus there is formed .a spaceinto which a portion of the sealing ring may be compressed. Inthespecial form of double curved sealing surface described, the inner toresealing surface operates to hold an adjacentsurface of the sealing ringin a sealed position with respect to a workpiece which is formedVwithout. any central opening and the relieved bottom affords @spaceinto which compressed portions of the sealing ring may be displaced whena workpiece is subjected to 'suction and held against the ilat face byatmospheric pressure.

`Similarly, the outer tore sealing surfaces function to hold an outersurface of the sealing ring in a sealedl position when it is desired tohandle a workpiece having `an annular shape and suction cannot beexerted within the ring `because of the hole at or near the center. In'this case a second outer sealing ring is used and suction re- :movesair from points circumferentially outside the inner ring and inside theouter ring the inner sealing ring takes atmospheric pressure pushingfrom the center outwardly, while the outer sealing ring takesatmospheric pressure pushingvfrom the outside radially inwardly.

Referring more in detail to the drawing, attention is directed to Figs.l and 2 in which numeral 2 denotes a wor'kholding element of circularshape and formed with a hat face 4. In the flat face are formed a seriesof special ring vretaining grooves having received therein elasticsealing rings as 6, 8, 10 and 12.

The'wor'k holding element is recessed to provide a plurality ofAradially extending passageways and each passageway is connected torespective axially extending passa'geways which communicate with spacesadjacent to the ring grooves of varying sizes referred to above. Thesepassageways are Vfitted with closure plugs so that one grooveor'passageway may be subjected to suction forces independently of allother grooves. In some cases a .given passageway may be closed byinsertion of a plug sothat suctionforces can be exerted only through apassageway occurring circumferentially outside of an inner sealing ringand inside of an outer sealing ring. This is particularlythe case whenit isdesired to use two sealing rings with workpiece having a hole -atyor near its centen lnother cases passageway may communicate with lonlyan opening occurring centrally inside of a seal.- ingring.' 'y ,eillustrative ofone simple form of air passageway forzaworkpiece ,YV-.1,having `no hole at or Ynear .it cen.-

' s'g'e'wa'y l'may' connect with an axial passageway 18'ocwithin an areaincluded by the Ysealing ring 6. Thus, whensuction forces are exertedthrough theseV passageways 14 and 18, the sealing ring is drawn radiallyinwardly. to form a seal, as islhereinafter described in'greater'detail..Y In Fig. 3 IY have shown anothersuctionjarrangementlin ,lajwork'holding element 2"hiViI1g an innensealing fring I6'Y and anouter Vsealing ringY f6 for` dealing with work pieceV W-Z which isannular inform and doesjhave a hole H atfor near its center. VThisAworkholdingelement is formed with air passageways-20 and In thisarrangement, lanair passageway20, suitably controlled rby aconventional'valve tting and c rmnectedto ais'uction pump, connects withan open axial passageway V2 2 lying between rings 6' and'6"butpassageway 24 is'sealed off by means of a threaded plug 23 having arubber gasl"liet 25 and, thus atmospheric pressure will push radiallyYinward Aagainst the ring 6"and radially outwardly' against the vring16.In this way, the inner sealing'ring is drawn Y radially loutwardlyagainstV an'adjacentrspe'cial groove surface while the Youter ringo isdrawn radially inrwardly against an adjacent groove surface.

' ',Considering inH greater detail the Vparts shown in Fig. V3,'annularwork piece W -2, as indicated therein, occurs Vin a completely sealedposition by means of rings 6' and` 6", being held byV atmosphericpressure againstthe work holdingrelement 2'. VIn this position,the'inner'elastic V`sealing ring 6 is compressed and sealed/in its 'ringretaining groove by atmospheric pressure acting on the ring in aradially outwardly directed manner and iby Vat'- 'mospheric `pressureacting on the outer'ring ina radial- Y `lyinwardly directed manner. j Yp Attention is directed to Fig. 5 in which Vis Vshowman enlarged view ofa groove construction of the invention which may be used for either asingle ring or two vring "type of sealing. As noted'therein numerals'30andf32 denote single curved surfaces of cylindrical form lying inconcentrically spaced relationship to one another.

acts in the opposite manner and seals against the surface Ydraws thesealing ring against the inner double curved .surface-34 with'the outerperipheral surface of :the sealing ring tending to draw away from thesealingnsurface 33. However, theV spaceV between the ringl and thebottomdouble curved surface 38 operates to receivewcompression of the ring-inYexactly the samermanner as Vwas the case with sealing an annular typeworkpiece.A `By the means described, therefore, I am enabled toV adaptthe single ring of toric section in any desired size to hold- .ing aworkpiece either of thepannular'or continuous form withequal'efiiciency. .Y

From the foregoing Vdescription it will be apparent that I havedisclosed an improved vacuumrtype chuck which has special adaptabilityto dealing with annularly shaped workpiecesand'which can, none the less,be appliedY with a good results Vto a workpie'ceof disc shape or otherunbroken form. Y l While ,I have shown a preferred embodiment Vof the`in- Y yention,itrwill be understoodV that various changesand 'Thesesurfaces correspond to similar surfacesbearing the Y'same referencecharacters in Fig. 3. As earlier described the space between thesesurfaces 32 vand 30 provide an entering aperture through which thesealing'ring 6' Vmay be inserted.

VVNumerals 33 and 34 denote the two* double Y' surfaces of theinvention. VThese surfaces 'comprise'n- Vner ,and'outer tore sealingsurfaces generated'by the'revo- 'lution' of a conic such as a circleaboutanaxis which lies inrits plane; which is parallel to A'the flatface 4';

and which is located below vthe flat face 4',"a distance Y flessfthanthe radius of thfe'conic. With :this Yradial re'- flationship thesealing -ring 6V when not under compressionwill extendslightly above thev surface of the flat face Vv4'- as shown in-Fig. 4.; Y

In accordance with the invention the distance between the double curvedsurfaces 33 and 34'measur'ed diametrically as shown in Fig. Y5 is chosenof a magnitude'cor- Yresponding 'to theV diameterV of a torio section oftheseal- Ving ring Vas is clearly illustrated Vin Figs. 3 and 4.Therefore, whenrthe sealing ring is crowded into the groove it will -lieinY contact withgeach of the double curved-surfaces 34 Vand 33 all theway around the groove.A However, whenV compression of theworkpiece W'-2Vis induced 'by suction and atmospheric pressure forces the'sa`lingringdownwardly, compressed portions of the sealingring l move into the"space `36 Vdefinedv bythe bottom'double curved surface 38 as suggestedin Fig. 3. v'Sirmiltan'e- 'the'realongV lou'sly with Atheringbeingcompressed -itisk drawn by suctionYV forces circumferentially`outwardly against the tore surface V33 to set up a tight seal with theinner 'periph- 1 eral portion of the ringY tending Yto move slightlyaway from the double curved space 34 A(Figure 3). .In; such apos'itionofsealing-it is pointed'out that thefpresence 'of theY closed hole H hasno effect upon-thevacuuniheld action of the chuck and thus angannularworkpieceW- Z 'may bel securely held. YThe outerV sealing ring, however,

modifications may be resortedto within;thescope of the appended claims.A Y Y jV Y v Having thus` described my invention, `what I claim is: l. Avacuum chuck for holding a workpiece of the class having Van opening`located centrally thereof, .said

vacuumVV chuck comprising a; work-holding element, `said work-holdingelement presenting a at face which ,is re- Vcessed to provide Vringretaining grooves, VelasticV sealing rings of torio` cross sectionvVarrangedfin concentrically spaced relationship ,toY "onel anotherginfthersiaidf ringy retaining groovesfeach'ofV said'grooves'beingdefined by a plurality,v of intersecting curvedV surfaces, including'`tw'o upper most single curvedjsurfaces of cylindricalshape lying inrconeentrically spaced relationship to one.another,

two doublecurved surfaces which intersect thesingle -curved surfaces,said double'curvedv surfaces being generated ybythe revolution-ofa'conic about an axis which lies at its plane; which isl parallelgtoVthe at'face of the lwork-holdingelement; which is located Abelow thefatface a'distance less than the radius of the conic,'and a third doublecurved surface occurring at the` bottom of theV groove to define a spaceinto which a respective elasvticy s ealing ring may be compressed when aworkpiece is .retained on the work 'retaininggelement 2Q Astructure-according to claim 1,'including suction means f or selectivelyexertingsuction forces whereby atmospherepressure may joperate'to pushan innermost 60 sealing ring radially outwardlyV against an adjacentgroove surface and whereby atmospheric pressure 'may operate to lpush anoutermost sealing ringradialiy inward against 'an adjacent groovesurface. v 3. A structure according to claim 2 in which the suc.- vtionmeans-includes air .passageways vand Ymeans for Aselectively closingthe'airfpassageways at separatedk points

